1. Field of the Invention
The present invention generally relates to communication apparatuses, communication control units, communication methods and computer-readable storage media, and more particularly to a communication apparatus, a communication control unit and a communication method which are suited for making short-range (or near) wireless communications using wireless local area network (LAN), blue tooth and the like, typified by a hot spot, and to a computer-readable storage medium which stores a program for causing a computer to make such short-range wireless communications.
2. Description of the Related Art
FIGS. 1 and 2 are diagrams for explaining an example of a conventional Internet protocol (IP phone system (SIP). FIG. 1 shows a general structure of the conventional IP phone system, and FIG. 2 shows a time chart for explaining an operation of the conventional IP phone system.
In FIG. 1, each of mobile terminals 101 through 103 are connectable to a server 100 via corresponding wireless routers 111 through 113 and a network 110 such as the Internet. The server 100 includes a proxy server Z that makes a calling destination location inquiry and the like, and a location server Y that registers and manages location information (position information) such as Internet addresses and telephone numbers of each of the mobile terminals 101 through 103. It is assumed for the sake of convenience that the Internet address, the IP address and the telephone number of the mobile terminal 101 respectively are “A@a.aaa.com”, “10.1.1.10” and “050-111-1111”, the Internet address, the IP address and the telephone number of the mobile terminal 102 respectively are “B@b.aaa.com”, “10.1.2.20” and “050-222-2222”, and the Internet address, the IP address and the telephone number of the mobile terminal 103 respectively are “C@c.aaa.com”, “10.1.3.30” and “050-333-3333”. In addition, it is assumed that Internet address and the IP address of the wireless router 111 respectively are “a.aaa.com” and “10.1.1.1”, the Internet address and the IP address of the wireless router 112 respectively are “b.aaa.com” and “10.1.2.1”, and the Internet address and the IP address of the wireless router 113 respectively are “c.aaa.com” and “10.1.3.1”. Furthermore, it is assumed that the Internet address of the server 110 is “aaa.com”, the IP address of the proxy server Z is “10.1.0.1”, and the IP address of the location server Y is “10.1.0.2”. It is also assumed that, when the mobile terminal 102 moves from its home location to an external location, the Internet address and the IP address of the mobile terminal 102 respectively change to “B@c.aaa.com” and “10.1.3.40”.
FIG. 2 shows a procedure P1 from a time when the mobile terminal 101 calls the mobile terminal 102 up to a time when a communication is made therebetween, and a procedure P2 for a case where location information is to be registered when the mobile terminal 102 moves from its home location to an external location.
In the procedure P1, the mobile terminal 101 makes a call, with respect to the mobile terminal 102 having the telephone number “050-222-2222”, to the proxy server Z. The proxy server Z makes a location inquiry related to the mobile terminal 102, to the location server Y. The location server Y returns a response with respect to the location inquiry, to the proxy server Z. The proxy server Z makes a call to the mobile terminal 102 based on the response (location information) from the location server Y. When an off-hook occurs at the mobile terminal 102 in response to a ringing, a response is returned to the proxy server Z, and the proxy server Z returns this response to the mobile terminal 101. The mobile terminal 101 returns to the proxy server Z a response with respect to the response received from the proxy server Z, and the proxy server Z returns the response received from the mobile terminal 101 to the mobile terminal 102. Accordingly, a communication becomes possible between the mobile terminal 101 and the mobile terminal 102, as indicated by a bold line in FIG. 1.
In the procedure P2, if the mobile terminal 102 moves from its home location (B@b.aaa.com, 10.1.2.20) to an external location having the Internet address “B@c.aaa.com” and the IP address “10.1.3.40”, the mobile terminal 102 can no longer maintain the connection with the mobile terminal 101 because the IP address of the mobile terminal 102 changes, and the connection is disconnected as indicated by a broken line in FIG. 2. The mobile terminal 102 which has moved in this manner makes a location registration of the external location with respect to the location server Y. When the moved mobile terminal 102 makes a call to the proxy server Z, the proxy server Z makes a location inquiry related to the mobile terminal 101 with respect to the location server Y. The location server Y returns to the proxy server Z a response with respect to the location inquiry received from the proxy server Z, and the proxy server Z makes a call to the mobile terminal 101 based on the response (location information) received from the location server Y. When an off-hook occurs at the mobile terminal 101 in response to a ringing, a response is returned to the proxy server Z, and the proxy server Z returns this response to the moved mobile terminal 102. Accordingly, a communication becomes possible between the moved mobile terminal 102 and the mobile terminal 101, as indicated by a broken line in FIG. 1.
FIGS. 3 through 5 are diagrams for explaining a conceivable mobile IP phone system, that is conceivable when the SIP system is applied to the conventional mobile IP phone system. FIG. 3 is a diagram showing a general structure of this conceivable mobile IP phone system, and FIGS. 4 and 5 are time charts for explaining an operation of this conceivable mobile IP phone system. In FIG. 3, those parts which are essentially the same as those corresponding parts in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted.
In the case of the conceivable mobile IP phone system shown in FIG. 3, home agents (HAs) 121 through 123 are provided in correspondence with the wireless routers 111 through 113 at the home locations of the mobile terminals 101 through 103. The HAs 121 through 123 register and manage location information related to the corresponding mobile terminals 101 through 103 at the respective home locations. Hence, even if the mobile terminal 102 moves from its home location, for example, the HA 122 at this home location manages the location information related to a present location of the mobile terminal 102, so that a communication with the moved mobile terminal 102 can be made via the HA 122.
FIG. 4 shows a procedure P11 from a time when the mobile terminal 101 calls the mobile terminal 102 up to a time when a communication is made therebetween, and a procedure P12 for a case where location information is to be registered when the mobile terminal 102 moves from its home location to an external location.
In the procedure P11, the mobile terminal 101 makes a call, with respect to the mobile terminal 102 having the telephone number “050-222-2222”, to the proxy server Z. The proxy server Z makes a location inquiry related to the mobile terminal 102, to the location server Y. The location server Y returns a response with respect to the location inquiry, to the proxy server Z. The proxy server Z makes a call to the mobile terminal 102 based on the response (location information) from the location server Y. When an off-hook occurs at the mobile terminal 102 in response to a ringing, a response is returned to the proxy server Z, and the proxy server Z returns this response to the mobile terminal 101. The mobile terminal 101 returns to the mobile terminal 102 a response with respect to the response received from the proxy server Z. Accordingly, a communication becomes possible between the mobile terminal 101 and the mobile terminal 102, as indicated by a bold line in FIG. 4.
In the procedure P12, if the mobile terminal 102 moves from its home location (B@b.aaa.com, 10.1.2.20) to an external location having the Internet address “B@c.aaa.com” and the IP address “10.1.3.40”, the moved mobile terminal 102 receives an advertising that is periodically made by the HA 123. In this case, a care of (c/o) address “10.1.3.40” of the external location is sent from the HA 123 to the moved mobile terminal 102. The moved mobile terminal 102 makes a location registration of the external location with respect to the HA 122 which is located at the home location of the mobile terminal 102. Accordingly, a communication becomes possible between the moved mobile terminal 102 and the mobile terminal 101 via the HAs 122 and 123, as indicated by a broken line in FIG. 3. In other words, the communication between the moved mobile terminal 102 and the mobile terminal 101 is made via the HA 122 that is located at the home location of the mobile terminal 102 and the HA 123 that is located at the external location where the moved mobile terminal 102 is presently located.
FIG. 5 shows a procedure from a time when the mobile terminal 101 calls the mobile terminal 102 up to a time when a communication is made therebetween, for a case where both the mobile terminals 101 and 102 have moved from their home locations before the call is made.
In the procedure shown in FIG. 5, the mobile terminal 102 located at an external location having a c/o address “10.1.1.40” make a call to the proxy server Z, and the proxy server Z makes a location inquiry related to the mobile terminal 101, to the location server Y. The location server Y returns a response with respect to the location inquiry to the proxy server Z, and the proxy server Z makes a call to the HA 121 that is located at the external location having the c/o address “10.1.1.40” based on the response (location information) received from the location server Y. For the sake of convenience, it is assumed that the mobile terminal 101 is located at an external location having a c/o address “10.1.2.40”. Hence, the HA 121 makes a call to the HA 122 that is located at the external location having the c/o address “100.1.2.40”, and the HA 122 makes a call to the mobile terminal 101. When an off-hook occurs at the mobile terminal 101 in response to a ringing, a response is returned to the proxy server Z, and the proxy server Z returns this response to the HA 122. The HA 122 returns to the HA 121 a response with respect to the response received from the proxy server Z, and the HA 121 returns the received response to the mobile terminal 102. Accordingly, a communication becomes possible between the moved mobile terminal 101 and the moved mobile terminal 102, as indicated by a bold line in FIG. 5.
However, according to the conventional IP phone system described above in conjunction with FIGS. 1 and 2, the IP address of the mobile terminal changes when this mobile terminal moves from its home location to an external location. For this reason, the connection of this mobile terminal with another mobile terminal to which a communication is being made cannot be maintained. Furthermore, since frequent moving of the mobile terminal was not assumed for the conventional IP phone system, there was a problem in that a location registration must be made to the location server every time the mobile terminal moves from its home location to an external location.
On the other hand, according to the conceivable mobile IP phone system described above in conjunction with FIGS. 3 through 5, when the mobile terminal moves from its home location to an external location, a communication with another mobile terminal is made via an HA located at the home location of the mobile terminal, an HA located at the external location where the mobile terminal is presently located, and an HA located at the home location of the other mobile terminal where the other mobile terminal is located. As a result, the need to communicate via a plurality of HAs causes congestion of the communication (communication congestion), and there was a problem in that a delay generated in the communication (communication delay) via the HAs is not negligible.